You could also check the offending/suspect file at:
VirusTotal - Multi engine on-line virus scanner I feel virustotal is the better option as it uses the windows version of avast (more packers supported) and there are currently 30 different scanners.
Or
Jotti - Multi engine on-line virus scanner if any other scanners here detect them it is less likely to be a false positive.
Whichever scanner you use, you can't do this with the file in the chest, you will need to move it out.If it is indeed a false positive, add it to the exclusions lists (
Standard Shield, Customize, Advanced, Add and Program Settings, Exclusions) and Restore it to its original location, periodically check it (scan it in the chest), there should still be a copy in the chest even though you restored it to the original location. When it is no longer detected then you can also remove it from the Standard Shield and Program Settings, exclusions.
Also see
False Positives, how to report it to avast! and what to do to exclude them until the problem is corrected.
